Ionospheric Response to Recent Strong Geomagnetic Storm at Low, Mid, and High Latitudes Using GPS-TEC Observations

The ionospheric response to the intense geomagnetic storm of 10–13 November 2025 is investigated using multi-latitude GNSS-derived total electron content (TEC), ground magnetic field observations, and geomagnetic indices. The storm was characterized by a minimum Dst of –230 nT and elevated Kp values exceeding 8, while the solar flux F10.7 remained relatively stable. Differential TEC (dTEC) analysis reveals a strong latitude dependence of storm-time ionospheric perturbations. Low-latitude stations exhibit relatively smooth variations within ±15 TECU, mid-latitude stations show enhanced and structured responses reaching ±30–35 TECU, and high-latitude stations experience the largest disturbances, with dTEC values exceeding –40 to –45 TECU during the main phase. Ground magnetic field data indicate increasing disturbance amplitudes with latitude, and wavelet analysis of TEC residuals shows enhanced power during the storm main and early recovery phases, with dominant shorter-period fluctuations at higher latitudes. These results demonstrate the significant latitude-dependent impact of intense geomagnetic storms on ionospheric TEC and highlight the importance of multi-latitude GNSS observations for characterizing storm-time ionospheric variability. Pre-storm analysis shows that TEC variability during the 2–3 days prior to the sudden storm commencement (SSC) remained comparable to quiet-time levels, with no coherent ionospheric precursor. These results demonstrate a pronounced latitude-dependent ionospheric response to intense geomagnetic storms and highlight the importance of coordinated multi-latitude GNSS observations for understanding storm-time magnetosphere–ionosphere–thermosphere coupling.